Various techniques have been used to improve the cold flow properties of diesel fuel compositions to meet climate-related requirements in diesel fuel specifications.
One way of improving cold flow properties is by the addition of middle distillate flow improver (MDFI) additives. However, the inclusion of such additives can increase the cost of the fuel. In addition, such additives will only affect cold flow properties such as cold filter plugging point (CFPP) and will not contribute to improved cloud point.
Another way of improving cold flow properties, and which also improves cloud point, is by blending conventional diesel fuel with refinery kerosene or Fischer-Tropsch derived kerosene. The addition of kerosene fuel lowers the cloud point of conventional diesel. However, Fischer-Tropsch derived kerosene and refinery kerosene have a low viscosity, typically below the minimum viscosity limit that is required in many diesel specifications. For example, Fischer-Tropsch derived kerosene typically has a viscosity of 1.3 mm2/s at 40° C. which is below the minimum viscosity limit of 2.0 mm2/s at 40° C. that is required in many diesel specifications (e.g. EN 590). Unfortunately, the low viscosity of kerosene fuel can limit the amount that can be added before the blend viscosity is reduced below the specification minimum viscosity requirements. In addition, Fischer-Tropsch derived kerosene and refinery kerosene have a low density (typically 810 kg/m3 or less for refinery kerosene and 800 kg/m3 or less for Fischer-Tropsch derived kerosene) which is below the minimum density requirement of 820 kg/m3 in many diesel specifications (e.g. EN 590).
It would be desirable to formulate a diesel fuel composition which enables target cloud point and cold flow properties to be met while ensuring that the final fuel formulation still complies with other specification requirements such as viscosity, density, distillation parameters, and the like.